This disclosure relates to offshore drilling and production operations in general and more specifically to a multi-cell reinforced concrete circular silo wherein ocean/lake drilling and production takes place.
Concrete offshore structures are mostly used in the petroleum industry as drilling, extraction, or storage units for crude oil or natural gas. Such large structures house machinery and equipment needed to drill and/or extract oil and gas. But concrete structures are not only limited to applications within the oil and gas industry. Several conceptual studies have shown recently, that concrete support structures for offshore wind turbines are very competitive compared to common steel structures, especially for larger water depths.
Depending on the circumstances, platforms may be attached to the ocean floor, consist of an artificial island, or be floating. Generally, offshore concrete structures are classified into fixed and floating structures. Fixed structures are mostly built as concrete gravity based structures (CGS, also termed as caisson type), where the loads bear down directly on the uppermost layers as soil pressure. The caisson provides buoyancy during construction and towing and acts also as a foundation structure in the operation phase. Furthermore, the caisson could be used as storage volume for oil or other liquids.
Floating units will be held in position by anchored wires or chains in a spread mooring pattern. Because of the low stiffness in those systems, the natural frequency is low and the structure can move in all six degrees of freedom. Floating units serve as productions units, storage and offloading units (FSO) or, for crude oil or as terminals for liquefied natural gas (LNG). A more recent development is concrete sub-sea structures. Concrete offshore structures show an excellent performance. They are highly durable, constructed of almost maintenance-free material, suitable for harsh and/or arctic environment (like ice and seismic regions), can carry heavy topsides, often offer storage capacities, are suitable for soft grounds and are very economical for water depths larger than 150 m. Most gravity-type platforms need no additional fixing because of their large foundation dimensions and extremely high weight.
The Deepwater Horizon oil spill (also referred to as the BP oil spill, the Gulf of Mexico oil spill, the BP oil disaster, or the Macondo blowout) is an oil spill in the Gulf of Mexico, which flowed for three months in 2010. It is the largest accidental marine oil spill in the history of the petroleum industry. The Deepwater Horizon rig is a fifth-generation, dynamically positioned, semi-submersible mobile offshore drilling unit capable in water up to 10,000 ft deep. The spill stemmed from the Apr. 20, 2010 blowout of the Mocando well resulting in loss of main power, explosions and uncontrollable fire onboard the Deepwater Horison. The disabled drill rig began to drift away from the wellhead and the drill pipe that was stretched between the rig and the well head separated at the blowout preventer increasing the flow of oil into the gulf. On Jul. 15, 2010, the leak was stopped by capping the gushing wellhead after it had released about 4.9 million barrels (780,000 m3) of crude oil. An estimated 53,000 barrels per day (8,400 m3/d) escaped from the well just before it was capped. The spill caused extensive damage to marine and wildlife habitats and to the Gulfs fishing and tourism industries.
Thus, while technology ever advances in permitting access to offshore oil deposits, drilling in such marine environments is not without substantial risks. There certainly is a need for oil drilling and production technology that minimizes the risks of incidents similar to the Macondo incident and exhibits much improved oil spill containment ability. It is to such need that the present invention is addressed, including a structure that can completely contain a 780,000 m3 oil leak.